Back pad coupling



Oct. 1956 B. TOCCFGUILBERT 2,767,527

BACK PAD COUPLING 27 [5a INVENTOR.

flip/v; 7050-604554 BACK PAD COUPLING Berne Tocci-Guilbert, San Francisco, Calif., assignor to Home Tocci-Guilbert, San Francisco, Calif., and Henry Gifiord Hardy, Berkeley, Calif., jointly as trustees Application December 29, 1953, Serial No. 400,989 4 Claims. (Cl. 51197) The present invention is a continuation in part of my copending application, Serial No. 149,138, which was filed March 11, 1950, issued as Patent No. 2,666,281, January 19, 1954 and is entitled Back Pad.

The present invention relates to improvements in back pad supports for use in connection with grinding and sanding discs, bufiing pads, grinding wheels and the like, which are normally attached to sanding, grinding and polishing machines, and particularly the invention is directed to a support which would provide an oscillatory movement, especially when applied to the work for fiat grinding, sanding or polishing and which will absorb the axial distortion and strain on the motor shaft and bearings when applied to the work at a point near the periphery of the grinding disc or working surface and spaced from the axis of the drive shaft.

The invention contemplates the employment of features formerly obtainable only with the addition of a special piece of equipment known as an oscillator and described in my issued Patents No. 2,633,008, No. 2,629,- 990, and No. 2,486,078, wherein the beneficial results of these pieces of equipment are obtained, but in a manner with the different structure disclosed herein, presently found to be an improvement thereover and to overcome some of the dificulties relating to earlier equipment.

It has been found that many of the beneficial results of the extended resilient facing of the structure shown in my application Serial No. 149,138, now Patent No. 2,666,281 could be obtained in an oscillator adapted for attachment to the spindle shaft of a sanding or grinding machine and for supporting the usual back pad conventionally used with surfacing discs or for direct attachment as a support for a grinding stone.

As disclosed in my Patent No. 2,629,990, a protective shell has been found desirable in order to control and limit the amount of oscillatory movement to that which is useful in the operation of this tool and to effect a protection for the resilient material itself against damage, chipping or any other destruction which would cause unbalanced rotation. However, providing a shell merely as an attachment has on occasion been found to be undesirable because of the independent movement between the shell, itself, and the resilient body, the loosening of the shell under axial distortion of working pressures, safety difiiculties and because of many more obtuse dithculties. Likewise, since the coupling is intended for use at high rotational speeds of from 1,800 R. P. M. to 5,000 R. P. M., the increase in modulus produces a high rate of gyrations. In order to secure uniformity of operation and uniformity of results, as well as the proper control, it has been found necessary to secure the shell to the driven hub. Accordingly, it is an object of the present invention to overcome these objections and criticisms and to provide a tool which is integral and which will at the same time perform in a similar, but greatly improved and safer manner.

nited States Fatent O It is the further object of the present invention to secure a wider face of rubber or other resilient material, for contact with the back pad without increasing the size of the shell, not only to give better support to the back pad but, among other things, to give a wider cross section of the rubber or other resilient material, for additional strength in the device itself.

Further objects are to provide a construction of maximum simplicity, economy and ease of assembly and fabrication, also such further objects, advantages and capabilities as will fully appear and as are inherently possessed by the device and the invention described herein.

The invention further resides in the combination, construction and arrangement of parts illustrated in the accompanying drawings, and while there is shown therein a preferred embodiment and one variant form thereof, it is to be understood that the same is merely illustrative of the invention and that the invention is capable of modification and change and comprehends other details of construction without departing from the spirit thereof or the scope of the appended claims.

Referring now to the drawings:

Figure 1 is a top plan view of the back pad coupling of the present invention.

Figure 2 is a vertical of Figure 1.

Figure 3 is a vertical section of a modification of the invention showing the coupling attached to a portion of a spindle shaft and with a back pad and sanding disc in position for working.

Referring now particularly to the drawings in which like reference numerals indicate like parts in the several views, the complete back pad coupling ready for attachment to the spindle shaft of a power tool as an integral unit, is shown generally in plan view in Figure 1 looking down on the top thereof.

In Figure 2, which is a vertical section taken on the line iI-II of Figure 1, the structure involved in the coupling is shown. In its final form the main body portion 10 is preferably of molded rubber, either natural or synthetic, but it is to be understood that it may be of any suitable resilient, flexible material. It is bonded to, molded and formed integrally with the several parts which are nonresilient and nonfiexible either in their function or structure, and Which are preferably metallic parts. The hub 11 is intended for attachment to the spindle shaft of a rotary tool for grinding, sanding, polishing or the like. It may be threaded as at 12 for attachment to the spindle shaft with the threads 12 being contra to the direction of rotation so that the device will tighten under rotary use, rather than loosening and endangering the safety of the operator. Such attachment, however, may be accomplished in any other suitable manner. The hub is provided with an internal flange 14 which not only section taken on the line IIII helps to key the body material in position, but extends outwardly into the mass itself.

Axially aligned with the hub 11 is a grommet 15. This grommet is likewise provided with outwardly extending internal flange 16 which presents a surface separated from, but opposed to the face of the flange 14. The grommet is preferably threaded internally as at 17 to receive the retaining nut 18. Even when the retaining nut 18 is completely received within the grommet 15, the inner terminus of the nut is separated from the hub 11 as well as the faces of the flange 14, so that there is never, at any time, any metal-to-metal contact. The grommet 15 is provided with an outer face 20 which extends laterally only a short distance, leaving a substantial exposed bearing face 21 of the resilient material which forms the body 10.

The device is sheathed by a substantially nonresilient,

preferably metallic shell 22. It is to be noted that the jshell 22 is directly attached to the hub 11 at 23 where lit is electrically velded or otherwise made completely lsecure to the hub itself. The cylindrical portion of the shell preferably terminates with a bell mouth 24, leaving a substantial peripheral flange of the resilient material 25 between the bell mouth 2% and the face 21.. This insures that there is no metahto-metal contact between the shell and the back pad when the coupling is in use.

In the manufacture of the coupling the shell 22 is welded or otherwise made secure to the hub 11 so that it is placed in the mold as a single part. The grommet is also placed in the mold in its relative position with respect to the hub and shell and rubber, either synthetic or natural, is molded and vulcanized to these parts so that when the parts are removed from the mold, it is a single integral unit with all of the metal parts bonded to the rubber or resilient material in a strong unitary structure. Accordingly, the word integral as used herein does not mean that the device can be assembled as parts on a shaft to form an operating unit, but is, rather, a complete unitary structure for use and attachment directly to the spindle shaft. The body of resilient material 10 fills the entire space within the shell and preferably provides a web 26 which unifies the two sides (as viewed in section in Figure 2) into a single interlocked mass. The web 26 also provides a strengthening of the internal structure of the complete unit, inasmuch as the shear stress due to the torque, normally occurs in the area where there is no lateral metal reinforcement. It should be pointed out, however, that the shell 22 reinforces the shear pointed out, however, that the shell 22 reinforces the shear strength laterally between the faces 14 of the hub 11 and the flange 16. The web, however, insures against any internal shearing and the possibility of any cleavage internally.

Referring now to Figure 3, the hub 11 terminates in an internal flange 14 and is axially aligned and spaced from the grommet 1511 by means of the resilient body material 10. It is to be noted that the shell 22 which is welded or otherwise permanently secured to the hub 11 at 23a terminates in a bell mouth 24a, which mouth extends from the top lateral surface 19. It is grommets outer face or flange extends laterally to a point coextensive with the terminus of the bell mouth 24a, so as to provide an abutting and supporting surface for the usual back pad and the abrasive disc 31. The retaining nut 18 holds the back pad 3t) and the disc 31 in frictional engagement against the exposed face 20a of the grommet 15a. The central portion of the retaining nut 18 is bored through as at 27. Likewise, the rubber body material 10 is left with an axial hollow center as at 28 so that no web is formed. This is to accommodate a situation where the coupling of the present invention is secured to a spindle shaft 32 by means of a screw 33. Here again, the threads of the screw 33 are countered to the direction of rotation. In order to attach a coupling on the shaft, it is necessary to use a tool through the openings 27 and 28. While, as indicated above, it is preferably to have the web 26 still, as shown in Figure 3, it is necessary to provide attachment of the coupling to the spindle shafts of such tools as have a threaded axial opening to receive the screw 35 as the only means for attachment. It will be observed that even in this circumstance the resilient body material is continued inwardly where the web would normally be formed, as much as possible, leaving only a sufficient diameter at 28 to accommodate the head of the screw 33. By doing this, the danger of internal stresses and shear are minimized internally while the shell 22 counteracts and reinforces against outward shear stresses.

Referring now to Figures 1 and 2, the purpose of the peripheral flange .25 is both structural and functional. In the first place, it presents a wider face of resilient material against and in support of the back pad 30 withalso to be noted that the.

out increasing the main outer diameter of the shell. In the second place, it gives a better support for the back pad 30 by increasing the available area of the surface 21. It also gives a wider cross section of resilient material for strength. Providing a bell mouth 24 means that there are no sharp edges of the metallic shell to cut into and weaken the resilient material of the peripheral flange. This is likewise true of the bell mouth 24a of the coupling shown in Figure 3.

It is also of importance of the exposed face 2t) of the grommet 15 provides both rigid and resilient contact for bearing against and supporting the back pad 30. This is an important feature as it permits resilient bearing and support to the back pad 30 in the areas of greatest axial distortion, while the metal bearing and support is against the area adjacent the axis.

As in my application Serial No. 149,138, the interposition of this coupling, when attached to the spindle shaft of a tool between the drive and the back pad the working surface of an abrasive disc held in position for rotation by the retaining nut 18 or between a stone held in position by the grommet 15, produces a nonmetallic resilient cushioned coupling, which sets up a vibratory oscillating torque when under working conditions the tool is applied to a work surface either in grinding, sanding, polishing or similar operation. This causes a butiing and nutative action in addition, which breaks the concentric lines of rotation of the tool when working pressure is applied. The absence of concentric grinding torque prevents the burning and deep scoring of any surface as well as eliminating the buffing rings. Flat grinding, sanding and the like is essentially not possible without the oscillatory action provided for herein. The frictional torque is either, greater than the operator can hold when pressure is applied to the work or else it stops the motor. Likewise, in the absence of oscillatory, nutative action, the abraded material, especially when used in surfacing marble, cork, rubber, or other soft surfaces, remains under the working area of the abrasive and there is not enough motionto cause it to be thrown aside. This results in the filling up and fouling of the abrasive material and requires frequent replacement of the cutting or surfacing material. With the gyratory, nutative movement provided for herein it is impossible to apply pressure at any one point and, therefore, even under heavy working pressures it is completely practical to use the entire face of the abrasive without arresting the speed of the motor or danger of jerking the tool from the control of the operator. Likewise, the abrasive is never filled or fouled because the movement constantly throws the abraded particles to the side. The oscillatory, nutative movement of this back pad coupling in operation under work conditions is nonconcentric and totally unpredictable. When working pressure is applied the lower lateral surface 21 of the resilient material It}, presses against the back pad, or against the grinding stone and accommodates itself to any irregularities to provide a secure and yielding contact. This also equalizes the pressure throughout the entire mass of resilient material. The bell mouth 24 of the shell 22 does not limit or react adversely no matter what pressure is required and will not cut through or weaken the peripheral flange 25, which greatly extends the contact surface 21, as well as increasing the strength of the resilient section. .Thus, by using the support of the present invention, the speed and other benefits long desired in this art are not only possible, but entirely practical.

it is well-known that conventional grinding, polishing and sanding is done only with a small portion of the grind ing wheel or disc actually in contact with the material. This means that conventional grinding is done with the grinding pad or wheel at an angle to the work so that only about three-eighths of an inch of the perimeter of the ordinary sanding disc or grinding wheel is actually in contact with the work surface. The sides of discs used for this high speed work range from small five-inch discs to to observe that the reduction medium seven-inch discs and large nine-inch discs, although larger sizes h-ave been used for specific purposes. It will be noted, therefore, that the point Where pressure is applied against the work is spaced several inches from the axis of the spindle shaft of the motor. The resulting leverage inherently means that there will be axial distortion. In the conventional manner of mounting the back pad rigidly to the spindle shaft, the axial distortion is transmitted directly to the bearings and the motor. This results in excessive wear and damage to the tool. Even where the conventional grinding or sanding position causing axial distortion is used with the back pad coupling disclosed herein, such distortion is not transmitted to the spindle shaft of the motor because there is no rigid coupling between the grommet 15 and the hub 11. The resilient body and its web 26 yield under the axial misalignment of the grommet and the pressures exerted by the peripheral flanges 14 and 16, respectively. Likewise, it is to be noted that toward the perimeter of the coupling of the present invention where the distortion is usually greatest, the support contact is an exposed portion 21 of the resilient material it) and, therefore, this distortion is immediately transmitted to the main body and redistributed. Thus, any axial misalignment caused by working pressures between the hub 11, which is rigidly attached to the spindle shaft of the driving motor, and the grommet 15, as well as the supporting surface 21 are completely absorbed, compensated for and not transmitted to the shaft of the motor. The wear and damage to the motor and its bearings are eliminated and the loss of time and expense in connection with servicing such tools is reduced to a bear minimum.

However, whether the support is used for flat grinding or for the conventional angle grinding or surfacing, the jar and vibration resulting from working pressure against the object which is normally transmitted through the hands, arms and shoulders of the operator, bringing discomfort and early fatigue, is not experienced by the use of this back pad support, by eliminating the cause and by the absorption of certain stresses in operation.

The driving member or hub 11 is formed in axial alignment with the driven member or grommet 15 but in spaced relation due to being imbedded and bonded to the resilient body material 10. Likewise, the shell 22 is in dynamic balance with and a unitary part of the hub 11 is spaced from the grommet 15 by the body material 10 to which it is bonded. No metal-to-metal contact is possible either in flat operation or in axial distortion under presently employed operating conditions.

It will be seen that all of the objectives of the present invention and many more are obtained by the structure herein disclosed.

I claim:

1. An oscillating torque mounting for back pads with sanding discs and the like comprising an attachable integral unit adapted for interposed attachment between the spindle shaft of a power tool and the supporting back pad of the sanding disc, said unit comprising a nonresilient driving hub member for attaching directly to the spindle shaft having an internal flange thereon, a nonresilient driven hub member adapted to receive and retain the back pad and sanding disc in a plane perpendicular to its axis, in axial alignment with said driving hub but spaced therefrom and having an internal flange the face of which is opposed to but spaced from said first flange, a nonresilient shell member secured to said driving hub above said first flange the wall of which terminates axially in a bell mouth below said second flange, and a body of rubber molded within said shell and of substantially the same diameter as said shell, surrounding said hubs and forming a driving connection therebetween and with a peripheral flange adjacent the bell mouth of said shell, each of said nonbody.

2. An oscillating torque mounting for back pads with sanding discs and the like comprising an'attachable in- I tegral unit adapted for interposed attachment between the spindle shaft of a power tool and a supporting back pad of the sanding disc, said unit comprising a nonresilient driving hub member for attaching directly to the spindle shaft having an internal flange thereon, a nonresilient driven hub member adapted to receive and retain the back pad and sanding disc in a plane perpendicular to its axis, in axial alignment with said driving hub but spaced therefrom and having an internal flange the face of which is opposed to but spaced from said first flange, a nonresilient shell member secured to said driving hub above said first fiange the wall of which terminates axially in a bell mouth below said second flange, and a body of rubber molded within said shell, surrounding said hubs and forming a driving connection therebetween including a peripheral flange adjacent the bell mouth of said shell and of substantially the same diameter and an exposed surface area for gripping contact with the outer surface of a back pad, each of said nonresilient members being securely bonded to said rubber body.

3. An oscillating torque mounting for grinding stones and the like comprising an attachable integral unit adapted for interposed attachment between the spindle shaft of a power tool and a grinding stone, said unit comprising a nonresilient driving hub member for attaching directly to the spindle shaft having an internal flange thereon, a nonresilient driven hub member adapted to receive and retain the grinding stone in a plane perpendicular to its axis, in axial alignment with said driving hub but spaced there from and having an internal flange the face of which is opposed to but spaced from said first flange, a nonresilient shell member secured to said driving hub above said first flange the wall of which terminates axially in a bell mouth below said second flange, and a body of rubber molded within said shell, surrounding said hubs and forming a driving connection therebetween including a peripheral flange adjacent the bell mouth of said shell and of substantially the same diameter as said bell and an exposed surface area for gripping contact with the outer surface of a grinding stone, each of said nonresilient members being securely bonded to said rubber body.

4. Polishing and abrading apparatus of the character described, comprising axially spaced, concentrically arranged and downwardly concave upper and lower plates, an upstanding collar on said upper plate, a central hub for attaching to the spindle shaft of a power tool secured to said collar, said hub having an internal flange, an internally flanged hub on said lower plate spaced from but in axial alignment with said upper plate and hub, means for securing a back pad and abrasive disc or the like to the exposed face of said lower plate, and an annular body of rubber molded with and bonded to said plates forming a driving connection therebetween and having substantially the same diameter.

References Cited in the file of this patent UNITED STATES PATENTS 2,114,967 Myers Apr. .19, 1938 2,227,588 Kemp Jan. 7, 1941 2,281,722 Smith May 5, 1942 2,295,282 Mall Sept. 8, 1942 2,394,882 Weynand Feb. 12, 1946 2,439,751 Olsen Apr. 13, 1948 2,486,078 Tocci-Guilbert Oct. 25, 1949 2,629,990 Tocci-Guilbert Mar. 3, 1953 2,633,008 Tocci-Guilbert Mar. 31, 1953 2,666,281 Tocci-Guilbert Jan. 19, 1954 

